Thermal means of indicating temperature and electric failure



Dec. 22, 1953 J. N. M INNES ET AL THERMAL MEANS OF INDICATINGTEMPERATURE AND ELECTRIC FAILURE 1 Z n e/nar: Job 7 Mac Pa Filed Feb.12, 1951 f/mes u/ H. ye/"arc! Patented Dec. 2 2, 1 953 THERMAL MEANS OFINDICATING TEM- V 6 PERATURE AND ELECTRIC FAILURE John N. Maclnnes, Newfields, and Paul H. Gerard,

Newmarket, N. H.

Application February 12, 1951, Serial No. 210.566 6 5 Claims.

This invention relates generally to the class of electric signaling andis directed particularly to a system for use in .connection withbuilding heating and temperature indicating apparatus.

The object of the present invention is to provide a means of indicatingtemperature change and electric failure in connection with heatingapparatus, such as oil burners, to give notice of the failure ofelectric current controlling the operation of such apparatus and/or thedropping of the building temperature below a desired level.

Another object of the invention is to provide a signal system of thecharacter stated with means for indicating when a furnace is overheated,but functioning normally, without giving a false alarm. it

It is also an object of the invention to provide means for accomplishingthe stated results, embodying two signals one of which is active whenthe heating equipment is operating properly and the temperature iscorrect, the other signal coming into operation and the first becominginactive when the reverse conditions prevail.

A still further object is to provide a temperature operated switch inthe second or alarm signal circuit which is adapted to effect theintermittent energization of the latter signal when the current fails inthe principal circuit.

Still another object of the present invention 0 is to provide means forenergizing the alarm signal circuit either by battery or from an A. C.source with thermal switch means controlled by the A. C. for maintainingthe latter ready to energize the alarm signal but functioning uponfailure of the A. C. supply to put the battery supply in the alarmsignal circuit.

The present application is a continuation-inpart of our pendingapplication Serial No. 145,324, filed February 21, 1950.

The invention will be best understood from a consideration of thefollowing detailed description taken in connection with the accompanyingdrawing wherein the single figure is a diagrammatic layout of theelectrical system constituting the invention.

Referring now more particularly to the drawing the reference character[0 generally designates a portion of an outside wall of a building.

Exteriorly of the building is located, upon the wall or in any, suitablelocation, a suitable receptacle 12, in which are mounted, to be clearlyseen, the two signal lights l4 and I6, which are preferably,respectively red and green.

Within the building, is a two circuit controlling thermal switch,generally designated l8. This 2 switch comprises thetwo terminals 20 and22 belonging respectively to the green and red signal light circuitsabout to be described.

Between the terminals 20-42 is a bi-metal switch blade 24 carryingopposite terminals 26 for selective contact with the signal circuitterminals.

The numeral 28 designates a conductor forming one side of an electriccircuit receiving voltage from the twenty-four volt side of the heatingequipment controls. The most convenient source of such low voltage isthe stack control of the burner. 'Such stack control has such lowvoltage current available as long as the burner is functioning properlyand the power supply is not impaired. Since such stack control isstandard equipment used on all automatically controlled and firedheating systems, it is not thought that illustration or furtherdescription of the same is necessary.

This conductor 28 is connected to one side of the green signal I6 andthe opposite side of this light is connected by the conductor 30 to theswitch terminal 20.

The conductor 31 forms the other side of the signal circuit and iselectrically connected to the switch blade 24.

Connected across the conductors 28 and 3! is the conductor 32 andresistance 33, the latter being located to heat the bi-metal blade 24,thereby causing the element to fiex in a direction to engage one of itsterminals 26 with terminal 20 thereby keeping the light I 6 energized solong as the power remains on.

The value of the resistance 33 is suchthat should the room temperaturedrop a predetermined amount below normal, the heat from the resistancewill be inadequate toprevent the bimetal from cooling slightly, allowingthe contacts 2026 to open, breaking the current flow to bulb l6, andcausing contacts 22-26 to close and thus complete th circuit for thesignal lamp [4 as will be hereinafter apparent.

In the present system use may be made of a battery power source or atransformer connected with the power supply, for energizing the redsignal light. Both sources have been illustrated and use is made of athermal switch or relay, generally designated 34, for the purpose aboutto be described.

One side of the light I4 is connected by conductor 35 with the terminal22, while the other side is connected by conductor 36 with one side of abattery 31.

The relay 34.is of the same design' as the thermal switch, or relay, l8in that it comprises the two spaced terminals 38 and 39 and aninterposed bi-metal switch blade 40 carrying the two contacts 4|.

The transformer 42 comprises the primary and secondary coils 43 and 44,the primary receiving current from th power line, as will be apparent.

The secondary 441s electrically connected with the terminalgiifl byconductor 45 while the other side is connected by conductor 46 with theconductor 36 as shown.

Across the transformer secondary is connected the heater resistance 41which when.thepower supply is uninterrupted, is heatedinthetrans; formersecondary circuit and afiects the bi -metal blade 40 to keep thecontactstfi-M closed,

The numeral 48 generally designates a thermal control switch comprising;a,- bi meta-l; switch blade 49 having a contact 50 for coaction with acontact Contact 5| is connected by conductor 52 with the bi metalblade40 of the relay unit 34i while the blade 49 is connected try-conductortil with the bi-metal-bladei 4:of =the switch- I8 Connecteds between thebi-metalblade 49' and conductor-46 is a resistance heater '53. Thisoimetal-element 49- is lccatedmn and abscrbsheat from convector of theheating equipment and: is oi such value as'tomaintain the terminals, orcontacts, ill-51: closed when thefurnace tem-v perature is not above aselected; or normal, value. When thesurrounding temperature rises. abovesuch-normaivalue, however, thebitmetalzelement lie-affected tocauseseparation of thelcontacts Sta- 51. In such event, resulting fromoverheatingof the heating equipment, thelimit controls would. shutofiithelcurrent at thecontrolpanel andtboth-lights-would then beout,indicatingat oncetheLcharacter. ofrthetrouble.

The control-switch. 481 in the I present system has an additionalfunction; as. will become. apparent. in. the; following description ofoperation.

As preniously. stated. the. transformer. 42. will normally heat.resistance 4;! to. keep. contacts 38-4l closed so that all currentdemands by light; bulbdliwill be.met by the transformer 52.

Ifrthe.linelcurrentshould:fail so that; the trans. former 42 produces nocurrent, the resistance-i1 will; cool; thuslcansingthe bi-metal: bladeelement; Ail: toppen. contacts 3.8;.41l. and. close. CQl'l-ftactsiisiella sothe batterywill: supply: any. curremrdemands; ofwbulhl4,the. other sde of; the attery. from. conductor as bein connected: bycoudpctor .4 with the terminal, cit-contact, 39.

When currentastartse tdflow-i through contacts than, it: will;flow-through-heater 5}, it being understood; thatithroughs thecurrentfailure the erminals. on contacts,- are-ac. would, be. closed 50;'I'herheatina: qflresistance'iawill causethe. birm ta-l: blade is a.pen. the Contacts; sir- 51. stoppin current flQw..-tQ-.the red lighit... Resistance 53 will then. cool; and the. circuit Will be. rgqlqtldi o. ligh he ,.hl1lb.- Thus thesignal light will be flashedontandcfi;

In the-event ill-$118. closingof theredsienal light circuit,- for some.reason other than power line failure, such, for:- example, as thedropping or temperature to a degree which would permit the bi-metalswitchblade-24 to closecontacts 2 2-2 6, the transformer-would maintancontrol and'supply currentfor the red light. The resistance 53, would;however, talrecfi some current from the light c r uit. nd: t e t; he ping. and c ofthe contacts 50-51, to flash the lght,as bec ste gt he. nra iori lig'sy ts n. t e. eve

condition that exists.

of power failure, overheating, failure to ignite properly, very poorcombustion, or any other fault that might cause the stack control tocutout, the low voltage current supplied by the circuit conductors28--3l, is shut off. When the supply of low voltage current is shut 01f,light It is extinguished and magnet I8 is deenergized allowing P ints Z622 to'closethus completing the circuit of lines 35and" 36, causing lightI4 to become energized and giving warning of the This action wouldaccomplish all that is desired except for the fact that the majorityotheating installations the radiation is inadequate to take care of theoutput of the furnace. This brings about an overheating condition whichis prevented from becoming dangerous by a; limit control, notillustrated, which is a part of the standard oil burner circuit. Whensuch overheating condition occurs the limit control shuts ofi the burnerby cutting off the power supply to the stack'control; thuslshuttingoffithe low-voltage supply; When this. latter action: oc-. curs thereaction, as-fares the present-,signahdevice is concerned, will. be thesame. as. a burner. failure in thatthegreen light it: will gooutandthered light lfiiwili come on. This, however, is undesirable inasmuchasoverheating is a common occurrence and is. not considered: dangerous.and will correct its-elf: as'soon as-the-furnace. cools off apredetermined.amount.

To eliminate the possibility. of false alarms" which would result from.the. overheating condition, thermal element 48: is installed on. ornear, a heat convector so that, inv the event of over-. heating, thebimetallic element 45% will open: con-. tacts 50-51 and will prevent a.complemv circuit from becoming established in the circuit 35-46, so thatlight It cannot givea false alarm. Thus in the event of overheating,green light IE. will go out butred light i4 Will:not light duetotheaction of thermal element 48; Thusif circuit 35-36 is renderedincomplete by either, or both, the action of the'r-mal element-49 orthgbimetal element 24, the light 14 will not beenergized.

It the low voltage supply from the stackcontrol on circuit 28- -31- isshut off due to the stack control cutting out} as a result of: afaultyburner, or is shutoff; due to power line failure, the convector whichunit 4flis on or near, wil1 be relatively. cool: and thusthebimetallicelement 45 will allow contacts 5fi,5-l' to remain closed, thusactionof elementZgi will complete thefcircuit to energize light [4,-which is proper.

h stack. o t l,v h rcinb re referred. s a standard unit as previouslystated which is commonly used, l. automatica ly ontr lled a r d heatingyestems All: of. h e sta c n r embod a za cltsupnly. hhliisd d from atransformer withnvhichsaid;stacl; concls re. norma ly au ppe lathe. resnt ven cn he ta s control-se ves nl asasg r f rr n sup y. to ac ua e.he. p es nt gi enio hein entiqn tse do not. many was. fiec heoerationQithest ck nirol.

The invention has been thus iiar, described in e ection wit tsutcwihheatina equipme employing a stacl; controlunit but it"is'also de;signed. r s h aut matic easfircd heate and w e ccm lc ed hecircuitwires. 8:31

would be connected to, the solenoid valve circuit,

n s c a mo t gas red heati gunitsare not qu pn w t steck-c ntrols- I Weclaim;

. 1.. e ns for. ndica in cu r nt a ure a princi al lectrici c itomn isia two electric signals, a separate operating circuit for each, one ofsaid circuits drawing current from said principal circuit, a thermalrelay including a terminal for each circuit and a bi-metal switch bladecommon to the two circuits for the selective closing of said circuits bycontact with one or the other of said terminals, a resistance heaterconnected across the principal circuit, said heater when energizedaifecting said bi-metal blade to maintain the said one circuit closed,and a source of electric potential for the other one of the circuits,said resistance heater being of such value as to be ineifective toinfluence the bi-metal element suificiently to maintain the said onecircuit closed upon depression of the temperature of the surroundingatmosphere below a predetermined value.

2. Means for indicating current failure in a principal electric circuitcomprising two electric signals, a separate operating circuit for each,one of said circuits drawing current from said principal circuit, athermal relay including a terminal for each circuit and a bi-metalswitch blade common to the two circuits for the selective closing ofsaid circuits by contact with one or the other of said terminals, aresistance heater connected across the principal circuit, said heaterwhen energized affecting said bi-metal blade to maintain the said onecircuit closed, a source of electric potential for the other one of thecircuits, and a closed thermal switch in the said other one of thecircuits, the last mentioned switch having a heat responsive element ofa value to effect the opening of the last named switch upon a rise intemperature of the surrounding atmosphere above a predetermined degree.

3. Means for indicating current failure in a principal electric circuitcomprising two electric signals, a separate operating circuit for each,one of said circuits drawing current from said principal circuit, athermal relay including a terminal for each circuit and a bi-metalswitch blade common to the two circuits for the selective closing ofsaid circuits by contact with one or the other of said terminals, aresistance heater connected across the principal circuit, said heaterwhen energized affecting said bi-metal blade to maintain the said onecircuit closed, a source of electric potential for the other one of thecircuits, and a closed thermal switch in the said other one of thecircuits and having a heat responsive element maintaining the last namedswitch closed while the surrounding atmosphere remains below apredetermined temperature, the last named switch further including aresistance heater connected across the said other circuit and inproximity to the last named heat responsive element to heat the latterwhen the said other circuit is closed whereby said other circuit will bealternately opened and closed.

4. Means for indicating current failure in a principal electric circuit,comprising an electric signal unit connected in series in said circuit,a thermal switch including a bi-metallic element and two terminals withwhich the element is adapted to selectively engage, said element and oneterminal when in engagement being in series in said circuit, a secondelectric circuit, a second electric signal unit in series in the secondcircuit, said bi-metallic element and the other terminal when inengagement being in series in the second circuit, a source of electricpotential in the second circuit, a heater element connected across thefirst circuit adjacent to and for heating the bi-metallic elementwhereby said element when kept at a predetermined temperature by theheater maintains electric engagement with the said one terminal, saidelement when below said predetermined temperature opening the principalcircuit and electrically engaging the said other terminal to close thesecond circuit, and a thermal switch in the second circuit functioningto maintain the second circuit closed when the atmospheric temperaturearound the last named switch is below a predetermined normal.

5. The invention according to claim 4, wherein the last named thermalswitch includes a heater element connected across the second circuit andfunctioning to raise the said atmospheric temperature above said normalwhen the second circuit is closed and the second signal unit energizedwhereby the second circuit will be alternately opened and closed.

JOHN N. MAcINNES. PAUL H. GERARD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,075,314 Flagg et al. Oct. 7, 1913 1,181,419 Williams May 2,1916 1,653,685 Whittington Dec. 13, 1920 2,439,331 Bean Apr. 6, 19482,511,631 Gordon June 13, 1950

